449/449-2 Log/Lin Ratemeter

Low-rate counting from <10 counts per second to 10 million counts per second

The ORTEC Model 449 Log/Lin Ratemeter provides two modes of operation: linear and logarithmic. The linear mode has 11 full-scale ranges from 10 to 106 counts/sec in 1-3-10 steps. The 5-decade log mode covers the range from 10 to 106 counts/sec in a single span. These selections permit logical operation of the instrument when measuring low, medium, or high steady pulse rates or when monitoring rates that vary through a wide range.

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The unique, circular front-panel meter provides excellent readability for both modes because of the longer effective scale inherent in its 240° movement and because of the 2% accuracy of its indications.

Zero suppression is provided for up to 100% of any linear range. Any relatively constant background in the counting rate can be subtracted from the data by adjusting this control. Also, a suppressed zero will permit observation of rates that are beyond the nominal full-scale limit with greater accuracy than could be obtained by switching to a higher range. The choices between 7 linear and 2 log time constants is a further aid in accurately reading the rate of incoming signals.

The Model 449 measures the rate of either positive or negative input signals with a wide variety of pulse shapes. This provides the user with maximum flexibility in the selection of sources for input signals.

In addition to the front-panel meter indications, outputs are provided for both current and voltage recorders, as well as a high-level voltage output for control or monitor applications.

The Model 449 is available with an optional built-in audible output (Model 449-2), which has a sound frequency that is variable as a function of count rate. The range of sound frequencies is effectively 0 to 500 Hz and corresponds directly to the full-scale range of the front-panel meter. The audible output includes a threshold control to totally suppress all sound until the input rate exceeds the preselected audio threshold and a separate audio volume control to allow either local or relatively remote audible monitoring of observed rates.

For control and/or alarm applications, the Model 449 can operate an accessory device through its analog input.

Specifications
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Performance

Linear

Ranges

11 ranges from 10 to 106 counts/sec full scale in 1-3-10 steps.

Dead Time

<100 ns on the 106 range; <0.3% of average pulse spacing up to the 3 X 104 range; ≤1% on the 105 and 3 X 105 ranges.

12-position switch selects the full- scale range and either linear or logarithmic mode; linear ranges are 0 to 10 counts/sec through 0 to 106 counts/sec in 1-3-10 steps; log range is 10 to 106 counts/sec.

TIME CONSTANT

9-position switch selects an integrating time constant of 0.03, 0.1, 0.3, 1, 3, 10, or 30 s for linear ranges from 10 to 3 X 104 counts/sec or for any of these values divided by 10 for 105, 3 X 105, and 106 ranges; Short and Long for the log range.

ZERO SUPPRESSION

10-turn precision potentiometer to suppress the zero-reference level for any linear range from 0 to 100%; the same full-scale span is effective above the preselected zero-reference level.

This option is in addition to the regular specifications of Model 449.

Audio Output

A tone of variable frequency is furnished through a chassis-mounted speaker; the frequency increases from essentially 0 to 500 Hz, corresponding to the proportional meter deflection.

Audio Threshold

A 1-turn control mutes the audible output until the input rate exceeds the setting of the control and permits the output to be heard for all higher rates; range is 0 to 100% of selected full scale, linear, and log.

Audio Volume

A 1-turn control adjusts the amplitude of the audible output from a near-inaudible level to a level that can be heard above normal laboratory ambient noise.